Electrode



- Oct. 13, 1931. I 1.. W. LAUB E Y ,8 7, 9

ELECTRODE Original Filed June 6, 1929 INVENTOR Louis Wilbur Liubc.

ATTORNEY .5 v

Patented Oct. 13, 1931 UNITED STATES PATENT OFFICE LOUIS WILBUR LAUBE,OI EAS'ILCLEVELAND, OHIO, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO FLEXLUMECORPORATION, OF TONAWAND'A, NEW YORK, A CORPORA- 'IION or new YORK\\ELECTRODE Application filed June 6, 1929, Serial No. 368,813. RenewedMarch 3, 1931.

This invention relates to electrodes for luminous electrical dischargetubes of the type employing an inert gas such as neon as the currentconducting medium, such tubes being extensively used for illuminatedsigns. The present invention relates particularly to cup-shapedelectrodes which have their open ends sealed to the open endsof a glasstube and form closures for the ends of the tube.

The interior surface of the glass tube receives a negative charge byreason of the fact that some of the electrons find lodgment thereon. Itis a property of the conduction of electricity that the electric currentat one point along the conductor tends to follow a path normal to anequipotential surface. In an electrical discharge tube, the receivingsurface of the electrode, whatever its form, is equipotential. In movingaway from the surface of the electrode, further equipotential surfacesexist which at first follow the surface of the electrode very closely,but are deformed as the distance from the electrode increases until theytake the form which exists in the main body of the tube which, owing tothe charge on the glass tube, is convex to the stream of ions. Passageof the stream through the convex equipotential surfaces tends toconcentrate the stream of ions toward the longitudinal axis of the tubealthough this is opposed by the mutual repulsion of the electrons.Inside the cup-shaped electrode, however, the curvature of theequipotential surfaces is reversed so that the stream of ions tends tospread outwardly to the wall of the electrode.

In the case of cup-shaped electrodes with the edge of the cup fused tothe edge of glass tube, there is a tendency for the stream of ions tospread as it passes into the electrode so that a large proportion of thestream strikes the electrode close to the seal, the concentration of theelectron stream at the edge of the glass seal causing excessive heatingat this point which is objectionable since the seal is the weakest pointof the structure.

The present invention has for its object to provide a cup-shapedelectrode which is of such form that concentration of the stream of ionsadjacent the seal connecting the open end of the electrode to the openend of the glass tube is prevented.

With the above and other objects in view, the invention may be said tocomprise the electrode as illustrated in the accompanying drawingshereinafter described and particularly set forth in the appended claims,togetherwith such variations and modifications thereof as will beapparent to one skilled in the art to which the invention appertains.

Reference should be had to the accompanyr. ing drawings in which:

Figure 1 is a sectional view showing a portion of the glass tube withthe electrode of the present invention attached thereto.

Fig. 2 is a diagrammatic view illustrating the effect of the electrodeon the electronic stream.

The glass tube which may form a part of an illuminated sign of the neontube type is indicated by the reference numerall and the cup-shapedelectrode is indicated generally by the reference numeral 2. Theelectrode is preferably formed of copper and may be made from a piece ofcopper tubing, the outer end portion of the electrode being formed byswaging the tubing to a small diameter to provide a stem 3, andenlarging the tubing above the stem to provide an enlarged portion 4 ofthe globular form of greater diameter than the glass tube 1.

A series of heat radiating fins 5.may be attached in a suitable mannerto the stem. In its inner end, the electrode has a cylindrical edgeportion 6 which is of a diameter-to fit upon the exterior of the glasstube which is sealed to the edge of the electrode by fusion, as wellunderstood in the art. The portion of the electrode above the stem 3 iscup-shaped and the side wall is bulged outwardly immediately below theend of the glass tube. The portion of the side wall of the electrodeimmediately below the end of the glass tube is thus curved outwardly sothat the exposed interior surface flares outwardly from the end of theglass tube.

As above explained, the equipotential surfaces adjacent the surface ofthe electrode conform closely to the surface of the electrode andgradually decrease in curvature as in I the glass tube flares away fromthe tube, the

deflection of the stream of ions at the mouth of the electrode isconsiderably decreased with the result that a large proportion of thestream passes into the electrode past the seal and is distributed quiteuniformly over the interior surface of the electrode without anyobjectionable concentration of the stream along the edge of the seal.

By reason of the fact that, during its passage through the glass: tube,the stream of ions is concentrated centrally of the tube, a considerableportion of the stream would normally be concentrated upon the centralportion of the bottom of the electrode. In order to disperse thisportion of the stream of ions over a greater area of electrode surface,a recess 7 of small diameter extending into the stem may be provided atthe bottom of the cup-shaped portion of the electrode.- Ions adjacentthe axis of the electrode passing into the recess 7 are deflectedlaterally toward the sidewall of the recess and are thus distributedover a greater area of electrode surface.

In Fig. 2 of the drawings, lines of travel of the ions are indicated bythe dotted lines a and successive equipotential surfaces within the tubeand electrode are indicated by the dotted lines 6.

As shown in this figure, the equipotential surfaces 7) within the glasstube are convex to the stream of ions and within the electrode concavethereto.

By reason of the outward flare of the in terior surface of the electrodeimmediately adjacent the end of the glass tube, the change inequipotential surfaces from the convex to concave with respect to thestream of ions is less abrupt than with the cup-shaped electrode ofuniform diameter so that the speading of the stream entering theelectrode is lessened and a greater proportion of the ions strike theinterior surface of the electrode well below the seal. Also, as thecentral portion of the stream of ions approaches the flaring mouth ofthe recess 7, there is a spreading of this portion of the stream whichis thus distributed over a considerably greater surface. area than itwould be if the bottom of tfihe electrode cavity were flat orsubstantially It will thus be apparent that the electrode of the presentinvention is of such form that the stream of ions will be distributedquite uniformly over the interior surface and local heating effects arethereby eliminated.

Furthermore, it is to be understood that the particular form ofapparatus shown and described, and the particular procedure set forth,are presented for purposes of explanation and illustration and thatvarious modifications of said apparatus and procedure can be madewithout departing from my invention as defined in the appended claims.

What I claim is:

1. An electrode for luminous discharge tubes adapted to seal the end ofa glass tube and having an open end of a diameter to fit over the end ofthe glass tube, said electrode being enlarged outwardly of the open endthereof to provide an interior surface flaring outwardly from the end ofthe glass tube.

2. An electrode for luminous discharge tubes adapted to seal the end ofa glass tube and having an open end of a diameter to fit over the end ofthe glass tube, said electrode being cup-shaped, of greater diameterthan the glass tube and of substantially globular form.

3. An electrode for luminous discharge tubes adapted to seal the end ofa glass tube and having an open end of a diameter to fit over the end ofthe glass tube, said electrode being cup-shaped, of greater diameterthan the glass tube and of substantially globular form, said electrodehaving a recess of relatively small diameter in the bottom thereofsubstantially in axial alinement with the end of the glass tube to whichthe electrode is attached.

In testimony whereof I affix my signature.

LOUIS WILBUR LAUBE.

